Nick Clegg may have enjoyed a more favourable press recently but the Sunday polls make grim reading for the Lib Dem leader. A ComRes poll[3] puts Clegg's party on 10 per cent, while the latest YouGov poll[4] has them on just seven per cent (their joint lowest rating since the general election), with Ukip snapping at their heels on six per cent. If repeated on a uniform swing at the election, the YouGov figues would reduce the Lib Dems to a rump of nine seats. The much-touted "differentiation strategy" has yet to bear fruit.

Ahead of the Budget, however, low poll ratings are something of a blessing for Clegg. The weaker the Lib Dems' poll ratings, the stronger his negotiating hand. As James Forsyth reports in today's Mail on Sunday[5], the Tories are fearful that the Lib Dems could exit the coalition as early as the start of 2014 (a possibility increased by poor poll ratings) and are determined to keep them on board. In this case, that means giving Clegg at least some of what he wants in the Budget.

The Lib Dem leader is still pushing for an accelerated increase[6] in the personal allowance (with the added support of Ed Balls[7]) funded by a £16bn package of tax rises[8] on the wealthy. On Monday night, David Laws, the Tories' favourite Lib Dem (and the only Lib Dem backbencher not to have rebelled in this parliament), will return to the fray[9], giving a major interview to Newsnight and supporting Clegg's demands, including the introduction of a "mansion tax" on properties worth more than £2m.

At present, it seems likely that Osborne will offer an accelerated increase in the personal allowance, which is due to rise from £7,475 to £8,105 this April, without making the full leap to £10,000. This will be funded by clamping down on tax avoidance (Osborne could introduce a "general anti-avoidance rule", a law that would require corporations to receive clearance from HM Revenue and Customs on their tax plans before implementing them) and by closing various loopholes, rather than a mansion tax. The Lib Dems have yet to convince their coalition partners of the merits of taxing wealth more heavily[10] and income more lightly.